Highly specific unnatural base pair systems as a third base pair for PCR amplification.

Area of Science:

• Molecular Biology
• Synthetic Biology
• Biotechnology

Background:

• The expansion of the genetic alphabet is crucial for advancing DNA technologies.
• Artificial base pairs offer a route to novel genetic information storage and retrieval.
• Efficient and selective incorporation of unnatural base pairs into DNA via PCR is a key challenge.

Purpose of the Study:

• To develop and optimize highly efficient unnatural base pair systems for use in polymerase chain reaction (PCR).
• To assess the amplification efficiency and fidelity of hydrophobic unnatural base pairs, specifically the Ds-Px system.
• To fine-tune the Px base modifications to minimize misincorporation rates without compromising pairing selectivity.

Main Methods:

• Investigated hydrophobic unnatural base pair systems, focusing on 7-(2-thienyl)imidazo[4,5-b]pyridine (Ds) and modified 2-nitro-4-propynylpyrrole (Px) bases.
• Assessed PCR amplification efficiency and fidelity across various template sequence contexts and with different DNA polymerases.
• Quantified misincorporation rates of unnatural bases opposite natural bases and the overall selectivity of Ds-Px pairing during PCR amplification.

Main Results:

• Optimized Ds-Px pairing using Deep Vent DNA polymerase achieved extremely low misincorporation rates (0.005%/bp/replication).
• DNA fragments were amplified approximately 10^10-fold over 40 PCR cycles with Ds-Px pairing selectivity exceeding 99.9%.
• Over 97% of Ds-Px pairs remained intact after 100-cycle PCR amplification (10^28-fold amplification).

Conclusions:

• Highly efficient and specific unnatural base pair systems, like the optimized Ds-Px system, can be integrated into PCR.
• This technology significantly expands the capacity for genetic information storage and manipulation.
• The developed Ds-Px pair system provides a robust framework for novel biotechnological applications.